Volunteers rescue people from their flooded homes along Beamer Road in Houston on Sunday.

The massive tropical storm that stalled over Texas has triggered a massive governmental response, but there is no question that Harvey still has the upper hand. First responders have been overwhelmed by the scale of the disaster.

“Please don’t give up on us. None of us are going to give up,” Houston Police Chief Art Acevedo said at a news conference Monday.

The head of Houston’s 911 emergency system, Joe Laud, said the average number of callers on hold hoping to speak to an operator had dropped to 10 Monday morning after hitting 250 during the height of Sunday’s flooding. He said the system had handled 75,000 calls. Don’t hang up — he implored residents — stay on the line.

“We are processing the calls and hopefully help will be on the way,” Laud said.

Harvey, still churning near the Texas coast and now throwing rain bands deep into Louisiana, has exposed what Houstonians already knew: Their city, the nation’s fourth largest, was a disastrous flood just waiting to happen.

But Harvey has also raised questions about how federal, state and local agencies should prepare for, and respond to, natural disasters. There were mixed messages from the state capital and Houston’s City Hall about whether to evacuate millions of people in advance of Harvey’s landfall, when it was a Category 4 hurricane.

Having learned lessons from Hurricane Katrina’s aftermath in 2005, the Federal Emergency Management Agency ­pre-positioned many of its personnel in advance of the storm, as did the Red Cross and other organizations. But when the floodwaters rose, people were still largely on their own. Some rode to shelters or hospitals in the back of city garbage trucks while others waded through chest-deep water on foot.

A neighborhood in Friendswood, Tex., was so heavily flooded by Hurricane Harvey that some people are using boats to travel through it.

FEMA said Monday that it already made major deployments of people and resources to Texas, including about 900 personnel in search-and-rescue teams, a million liters of water, a million meals, 20,520 tarps and 70 generators. FEMA is coordinating a response that includes the National Emergency Medical Services, which is deploying 100 ambulances and 15 air ambulances out of San Antonio. FEMA has 1,800 personnel deployed in total along with 341 personnel from the Department of Homeland Security.

Leaders of the federal response to the Hurricane Harvey disaster had an early-morning news conference Monday in Washington that was by turns a declaration of competence, an expression of grave concern and a plea for the public’s help.

“Under the president’s direction, we have made every resource available to respond to this historic storm,” said Elaine Duke, acting secretary of the Department of Homeland Security, who added that on Tuesday she will accompany President Trump on a visit to Texas, where he plans to tour flood-ravaged areas.

Joining Duke at FEMA headquarters were William B. “Brock” Long, the FEMA administrator; Louis Uccellini, director of the National Weather Service; Tom Price, secretary of the Department of Health and Human Services; and Adm. Paul F. Zukunft, commandant of the Coast Guard.

Long, preparing to fly to Texas as soon as the news conference was over, said the situation in Texas was not yet a “recovery” operation but rather still a “life-safety” operation in which a primary focus will be taking care of what he estimates will be 30,000 people needing shelter. He later said that all estimated numbers are likely to change every 30 minutes.

“We’ve got to get them into shelters,” he said. “This shelter mission is going to be a very heavy lift.”

“Right now, here’s what I need you to know. Helping Texas overcome this disaster is going to be far greater than FEMA coordinating the mission of the entire federal government. We need citizens to be involved,” he said. “This is a landmark event. We have not seen an event like this. You could not draw this forecast up. You could not dream this forecast up.

“I’m asking for all citizens to get involved here. Donate your money. Figure out how you can get involved as we help Texas find a new normal going forward after this devastating disaster.”

Long deflected questions about whether Houston should have been evacuated.

“It’s not a time to start pointing blame,” he said, noting that Houston is a city with millions of people and not a place easily evacuated. “Pulling the trigger on that’s an in­cred­ibly difficult situation.”

Uccellini said Southeast Texas still faces another 15 to 20 inches of rain, but he cautioned that forecasting the storm is difficult. Harvey hit Texas late Friday and, as the National Hurricane Center predicted, came to a virtual halt. He said the center of circulation then migrated to a point over Matagordo Island, a barrier island on the Gulf Coast, not far from where Harvey made landfall Friday with 130 mph sustained winds.

Zukunft pointed out that search-and-rescue operations in this case are hampered by the continued presence of a storm that is producing heavy rain over a large area.

“We’re still operating in the midst of a tropical storm,” Zukunft said. “We have thrown every Coast Guard asset available at this response. But there are conditions where it’s just not safe to fly.”

Retired Adm. Thad Allen, who played a key role in shoring up the initially weak federal response to Hurricane Katrina in 2005 and then served as national incident commander for the gulf oil spill in 2010, said government agencies seem to be doing their best in an extremely complex situation that is huge in scale.

“I’m not sure how much more you can ask for,” Allen said. “If you have more total fires than you have firemen, the scale, complexity and scope becomes a risk aggregator. The demand signal for what you do far outweighs the resources you have.”

But second-guessing is rampant about whether officials in Houston should have ordered evacuations.

NICK OXFORD

REUTERS

Evacuees are transported Sunday to the George R. Brown Convention Center in Houston.

Michael Brown — who ran FEMA under President George W. Bush, and was criticized for the agency’s response during Katrina — said local officials should have done more to encourage people to voluntarily leave ahead of the storm.

“I think it would have been wise, it may have been smart to get in front of the media and talk about, ‘Here’s what I’m being told. We’re not going to order a mandatory evacuation, but our advice is, if you can leave now, you should leave,’ ” Brown said. “Is it better to be stuck in Dallas than to be stuck in the Houston convention center? Personally, for me I’d rather be stuck in Dallas than with 5,000 people in a convention center.”

Weather forecasters knew Tuesday that the tropical depression in the Gulf of Mexico might blow up into a hurricane, and by Thursday morning, they knew it might turn into a storm with winds that would rate it as the most powerful to hit Texas since Hurricane Carla in 1961. But on Sunday, there were elderly people still in nursing homes in places barely above sea level, many hauled to safety by the desperate efforts of ordinary citizens in private boats.

“It’s really the poor and vulnerable population that needs to be shifted to shelters, and all that needs to be done in advance,” said Patrick Roberts, a Virginia Tech professor who teaches about disaster response and is a native of Victoria, Tex.

Social media proved to be crucial piece of infrastructure during the storm. The national and local news media covered the unfolding disaster extensively, but social media allowed residents to figure out how their own neighborhoods were faring, who needed help and who had a boat or some other resource to deploy.

Two aspects of FEMA’s initial response bear the hallmarks of post-Katrina reforms. First, the agency deployed hundreds of personnel into Texas ahead of the storm to be in position to respond faster after the storm passed.

“That was the authority we got post-Katrina that FEMA could begin pre-deploying and spending money prior to a request from a governor if an event has occurred or is likely to occur requiring federal assistance,” W. Craig Fugate, the FEMA administrator under President Barack Obama, explained. “It’s part of the reason we have our regional office. We see something like this coming, FEMA will get those teams into those states and if we start getting the potential impacts, we’ll set up an incident staging base and start moving supplies and resources before the storm gets there. Hurricanes are one of the few things we can do that for.”

Fugate also said that he’s proud to see the swift deployment of FEMA’s urban search-and-rescue teams that are now equipped to handle water rescues. Previously when FEMA deployed search-and-rescue teams, “they weren’t equipped for water rescues. I was asking the question, ‘Why not?’ So, in the Obama administration we began equipping urban search-and-rescue teams with swift water rescue capabilities. The first time we actually used that was last year during the response to Hurricane Matthew in Fort Bragg and surrounding communities.”

Fugate and Brown said FEMA and other federal agencies never contemplated or rehearsed for urban flooding on such a massive scale. Fugate declined to offer a review of how the response has gone so far.

Brown said he believes that the response has been “really good, but I’m still disappointed that Americans haven’t learned that Mother Nature is going to do what Mother Nature does.”

Jason McNamara, a former FEMA chief of staff, said Long is taking the right approach so far — in part by not fighting with local and state officials.

“When you start getting folks above you questioning where you’re going with things or what you’re doing, things tend to fall apart very quickly,” McNamara said. “If he screws up, that’s one thing. But I don’t see that. I see him doing what he needs to do.”

He said of Texas officials: “They’re overwhelmed by life-safety missions. Very quickly you’re going to get behind the curve on what comes next week. The other thing? Schools. How do we get the schools open and kids back to school? If they can’t go back to school, the parents can’t go to work and that creates another economic problem.”